1. Field of the Invention
The present invention relates to a production method for a composite substrate.
2. Description of the Related Art
It is expected to realize an unconventional elastic wave device operable at a high frequency by using a piezoelectric thin film having a considerably small thickness. Preferably, the piezoelectric thin film is a piezoelectric single crystal thin film having high crystallinity, an arbitrary crystal axis, and uniform thickness. As a method for obtaining such a piezoelectric thin film, for example, PTL 1 proposes that a piezoelectric-substrate side of a laminated substrate having a diameter of 4 inches or more and obtained by bonding a piezoelectric substrate and a support substrate is mirror-polished, data on a thickness distribution of the polished piezoelectric substrate is created, and ion beam machining is performed on the basis of the data on the thickness distribution.